Prop-heads set your Tivos on stun. PBS's "Nova" tonight will feature a look at last October's DARPA Grand Challenge autonomous vehicle race, on a episode it calls "The Great Robot Race." The program will follow contestants in the lead-up to the race followed by the competition, in which a Volkswagen Touareg named Stanley, built by the team of Stanford University and Volkswagen Electronics Research Laboratory (ERL) won by completing the 132-mile desert course in six hours and 35 minutes. Geek rating: A[sum(X[j]*Y[j], j=1,10)]+.